**6. Application of microbial biopesticides**

Majority of biopesticides that show a reduction of pest populations under controlled environments have not succeeded under field conditions [121]. This is due to that, application methods of biopesticides have not been effectively explored. Most of the equipment used to apply biopesticides were developed for synthetic pesticides and are not suitable for biorational agents [122]. The use of application


#### **Table 5.**

*Some of the commercially available biopesticides used to control cotton pests.*

equipment designed for uniform application of biopesticides such as air-assisted spraying is essential [123]. The design of methods for biopesticide application also relies on the material used and the shape of the crop canopy [124]. Therefore, thorough coverage of all the surfaces reached by a pest is required for effective control. Over and above the correct equipment, precise microbial inoculants are key for a successful biocontrol programme. Microbial biopesticides can be applied in the field as a powder or in a liquid form through seed treatment, root dip, soil or foliar application [125]. Biopesticides must be applied as per the instructions provided in order to apply the correct dosage and the amount of water. As the persistence of biopesticides is an important factor in their efficacy, the timing of application plays a crucial role in pest control. These biocontrol agents tend to be less effective when applied during hotter day times and high rainfall.

Therefore, applications may be were administered late afternoon due to the UV sensitivity of the biological agents [25]. Alternatively, ultraviolet (UV) absorbents or protectants are necessary to combat this degradation and protect the microbes from sunlight. The UV absorbents or protectants dissolves in the insect stomach and release the virus that kills the pest [126]. However, more commercial UV-resistant biopesticides need to be improved to be readily accepted by farmers. It is also important to carefully select a biopesticide specific for the pests that have to be controlled. Furthermore, the level of toxin in the selected biopesticide as well as the feeding behaviour of the target pest is essential to determine the efficacy of the product [127]. Some of the common trade names for commercially available microbial biopesticides are listed in **Table 5**, and many small manufacturers distribute similar biopesticides using different trade names.
